Dolphins running back Jay Ajayi didn’t make the trip to Seattle for Sunday’s season opener, and it was coach Adam Gase’s decision to leave him home.

Gase didn’t address the reason for that decision. The team’s injury report Friday listed Ajayi as out for the game, the reason being “not injury related.”

Ajayi, a 2015 fifth-round pick from Boise State was listed as the backup to Arian Foster on Monday when the official depth chart was released.

Gase, speaking after Friday’s walkthrough practice at the University of Washington’s Husky Stadium, said that even though Foster was listed as the starter, he viewed Ajayi as being right there in the competition for playing time.

“I guess I didn’t really see it as technically starter/backup, because the way I see it they it was going to be they were 1a, 1b,” he said.

Ajayi handled most of the running back duties with the first team throughout training camp and the preseason while Foster was brought along slowly as he recovered from an Achilles injury that ended his 2015 season.

Miami Dolphins cornerback Tony Lippet talks about overcoming his injury from last season.

Miami Dolphins cornerback Tony Lippet talks about overcoming his injury from last season.

CAPTION

Participants raise money for cancer research during the Dolphins Cancer Challenge at Hard Rock stadium. All of the participant-raised funds goes to innovative cancer research at the Sylvester Comprehensive Cancer Center.

Participants raise money for cancer research during the Dolphins Cancer Challenge at Hard Rock stadium. All of the participant-raised funds goes to innovative cancer research at the Sylvester Comprehensive Cancer Center.

CAPTION

Dolphins vice president of football operations Mike Tannenbaum said at the Senior Bowl that he wants to address every position in free agency to free the team up to take the best players available in the 2018 draft.

Dolphins vice president of football operations Mike Tannenbaum said at the Senior Bowl that he wants to address every position in free agency to free the team up to take the best players available in the 2018 draft.

CAPTION

Miami Dolphins general manager Chris Grier praised the growth Charles Harris and liked what his fellow rookies showed in 2017.

Miami Dolphins general manager Chris Grier praised the growth Charles Harris and liked what his fellow rookies showed in 2017.

Ajayi had a poor showing in the preseason finale against Tennessee, losing a fumble and dropping a pass. The depth chart came out four days later.

Gase was asked Monday about the decision to start Foster shortly after the depth chart became public.

“I think a little bit of the reason is experience,” he said. “But at the same time I think Arian, from the time he’s gotten here, has really shown that, that is the correct spot for him to be in. He had a really good camp.

“He did everything we asked him to do as far as what we wanted to see in the preseason and he’s been very consistent in his knowledge of the offense in the short period of time that he was here – it was impressive to watch him (and) how quickly he picked it up.”

WHO HAS THE EDGE? The Dolphins--with 38-year-old new coach Adam Gase--limp into the Pacific Northwest for their season opener with Pro Bowl center Mike Pouncey, starting linebacker Jelani Jenkins and second-year wide receiver DeVante Parker all questionable. Here are the matchups. -- Chris Perkins

The Dolphins have five running backs on their roster with Foster and Ajayi joined by Damien Williams, rookie Kenyan Drake and Isaiah Pead.

Gase said Friday that special teams would be a factor in how many running backs would make the 46-man gameday active roster.